Communication terminal apparatus and antenna device

ABSTRACT

An antenna device which includes a coil conductor and a booster conductor. The coil conductor is defined by wound loop-shaped conductors and includes a first opening at a winding center and two ends connected to a feeding circuit. The booster conductor includes a coupling conductor portion and a frame-shaped radiation conductor portion. The coupling conductor portion includes a second opening overlapped at least partially by the first opening, is split in a portion thereof by a slit, and is electromagnetically coupled to the coil conductor. The frame-shaped radiation conductor portion includes a third opening and is connected to the coupling conductor portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to communication terminal apparatuses andantenna devices. In particular, the present invention relates tocommunication terminal apparatuses and antenna devices that can be usedin a radio frequency identification (RFID) system.

2. Description of the Related Art

In recent years, an RFID system has been used as an article informationmanagement system. In an RFID system, predetermined information istransmitted between a reader/writer that generates an induction fieldand an RFID tag attached to an article, through non-contactcommunication based on an electromagnetic field. An RFID tag storespredetermined information and includes a wireless IC (feeding circuit)that processes a predetermined wireless signal and an antenna devicethat performs transmission/reception of a high-frequency signal.Further, various portable terminal apparatuses that include an antennadevice for an RFID system have been recently developed as near fieldcommunication (NFC) apparatuses.

Japanese Unexamined Patent Application Publication No. 2001-351083discloses a non-contact data carrier apparatus that includes anon-contact data carrier, provided with an antenna coil, and anauxiliary antenna for the data carrier. The auxiliary antenna includes aconductive sheet that is arranged outside of a position that is the sameas or substantially the same as the innermost circumference of anantenna coil. The area of one side of the conductive sheet is greaterthan or equal to the area surrounded by the antenna coil. The auxiliaryantenna is arranged near the antenna coil of the data carrier. However,in this non-contact data carrier apparatus, the conductive sheet, whichfunctions as a radiation plate, is solid and occupies a large space.Thus, other electronic components need to be mounted in a region otherthan the region of the conductive sheet, which results in low spaceefficiency and an increase in the size of the portable terminalapparatus.

Japanese Unexamined Patent Application Publication No. 2007-324865discloses an antenna circuit that includes an antenna conductor in whicha predetermined conductor pattern is provided on the top surface of abase member and a metal surface is arranged on the bottom surface of thebase member, where a portion of the metal surface is provided with acut-out portion that has a shape in which both a starting end and aterminating end of the cut-out portion are open ends in areas in whichthe metal surface does not exist. However, to obtain necessarycommunication characteristics, the metal surface and the antennaconductor must be increased in size, leading to an increase in theoverall size of the antenna, which is also due to the thickness of thebase member. Thus, other electronic components need to be mounted in aregion other than the regions of the metal surface and antennaconductor, resulting in low space efficiency and an increase in the sizeof the portable terminal apparatus.

International Publication No. 2009/142114 discloses a wireless IC devicethat includes a wireless IC chip which processes a predeterminedwireless signal, a feeding circuit substrate which is connected to thewireless IC chip and which includes a feeding circuit including at leastone coil pattern, and a radiation plate which radiates a transmissionsignal supplied from the feeding circuit substrate and which receives areception signal and supplies the reception signal to the feedingcircuit substrate. Further, FIG. 18 of International Publication No.2009/142114, for example, illustrates a radiation plate defined by afirst electrode including an opening and a slit and a radiation platedefined by a second ring electrode that surrounds the first electrode.However, since the second ring electrode completely surrounds the firstelectrode, the Q factor is likely to be low and there is room to improvethe communication characteristics. Further, in International PublicationNo. 2009/142114, there is no mention of improving space efficiency inrelation to other electronic components.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of thepresent invention provide a communication terminal apparatus and anantenna device having improved communication characteristics and inwhich other electronic devices can be arranged with high spaceefficiency.

A communication terminal apparatus according to a first preferredembodiment of the present invention preferably includes an antennadevice and an electronic apparatus that has a function different from afunction of the antenna device and that outputs information to theoutside or receives information from the outside. The antenna devicepreferably includes a coil conductor including a loop-shaped woundconductor that includes a first opening at a winding center, and twoends which are connected to a feeding circuit, and a booster conductorincluding includes a coupling conductor portion that includes a secondopening that is at least partially overlapped by the first opening, issplit in a portion thereof by a slit, and is electromagnetically coupledto the coil conductor, and a frame-shaped radiation conductor portionthat includes a third opening and is connected to the coupling conductorportion. The electronic apparatus is preferably arranged so as to outputinformation to the outside or receive information from the outsidethrough the third opening.

An antenna device according to a second preferred embodiment of thepresent invention preferably includes a coil conductor including aloop-shaped wound conductor that includes a first opening at a windingcenter, and two ends which are connected to a feeding circuit, and abooster conductor including a coupling conductor portion that includes asecond opening that is at least partially overlapped by the firstopening, is split in a portion thereof by a slit, and iselectromagnetically coupled to the coil conductor, and a frame-shapedradiation conductor portion that includes a third opening and isconnected to the coupling conductor portion.

In the antenna device described above, an induced current is generatedin the coil conductor through feeding of electricity from a feedingcircuit. This induced current causes an induced current to be furthergenerated in the frame-shaped radiation conductor portion through thecoupling conductor portion, and a magnetic field is generated from theframe-shaped radiation conductor portion, whereby communication with thereader/writer of an RFID system is performed. Since the boosterconductor is at least partially overlapped by the coil conductor in thecoupling conductor portion, an induced current is efficiently generatedand communication characteristics are improved. In particular, since theradiation conductor portion of the booster conductor has a frame shape,the Q factor of the coil conductor is significantly increased, and thecommunication characteristics are significantly improved.

Since the radiation conductor portion of the booster conductor has aframe shape (third opening), information can be input/output through thethird opening. For example, it is possible to take a photograph throughthe third opening by arranging a camera in the third opening, infraredcommunication with the outside is possible through the third opening byarranging an infrared communication apparatus in the third opening, andaudio messages, for example, can be transmitted to the outside throughthe third opening by arranging a loud speaker in the third opening. Inthis manner, by arranging an electronic apparatus in the third openingto output information to the outside or receive information from theoutside, high-density component mounting in a portable terminalapparatus is achieved.

According to various preferred embodiments of the present invention,communication characteristics are significantly improved and otherelectronic apparatuses can be arranged with high space efficiency.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of an antenna device according toa first preferred embodiment of the present invention.

FIGS. 2A-2C illustrate an antenna device according to the firstpreferred embodiment of the present invention, where FIG. 2A is adiagram explaining a current flowing through a coil conductor, FIG. 2Bis a diagram illustrating currents flowing through a booster electrode,and FIG. 2C is a magnified sectional view taken along line C-C of FIG.2A.

FIG. 3 is a diagram explaining currents flowing through a boosterconductor of a comparative example.

FIG. 4 is a graph illustrating the communication characteristics of anantenna device of the first preferred embodiment of the presentinvention and the comparative example.

FIG. 5 is an exploded perspective view of an antenna device of anothercomparative example.

FIG. 6 is a perspective view of the major portions of a portableterminal apparatus into which the antenna device of the first preferredembodiment of the present invention has been incorporated.

FIG. 7 is an exploded perspective view of a modified example of anantenna device of the first preferred embodiment of the presentinvention.

FIG. 8 is a plan view illustrating a modified example of a coilconductor.

FIGS. 9A and 9B illustrate an antenna device according to a secondpreferred embodiment of the present invention, where FIG. 9A is a planview of a state in which a coil conductor and a booster conductor arecombined and FIG. 9B is a plan view illustrating a state in which theyare taken apart.

FIGS. 10A and 10B illustrate an antenna device according to a thirdpreferred embodiment of the present invention, where FIG. 10A is a planview of a state in which a coil conductor and a booster conductor arecombined and FIG. 10B is a plan view illustrating a state in which theyare taken apart.

FIGS. 11A and 11B illustrate an antenna device according to a fourthpreferred embodiment of the present invention, where FIG. 11A is a planview of a state in which a coil conductor and a booster conductor arecombined and FIG. 11B is a plan view illustrating a state in which theyare taken apart.

FIG. 12 is an exploded perspective view of an antenna device accordingto a fifth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of a communication terminal apparatusand an antenna device according to the present invention will bedescribed with reference to the attached drawings. Note that commoncomponents and portions in the figures are denoted by the same referencesymbols, and duplicate descriptions thereof are omitted. Further, acommunication terminal apparatus is described as an example a portableterminal apparatus.

First Preferred Embodiment

Referring to FIG. 1, an antenna device 1A according to a first preferredembodiment of the present invention includes a coil conductor 10 and abooster conductor 20. The coil conductor 10 preferably has a two-layerstacked structure including an insulating sheet, which is notillustrated in the figure, between the layers, for example. Loop-shapedconductors 11 and 12 that are wound so as to be superposed with eachother in plan view are connected at ends thereof through a via holeconductor 13 a, thereby forming a single coil including a first opening14 at the center of the winding. Further, feeding terminals 15 a and 15b are connected to each other through a via hole conductor 13 b, andfeeding terminals 16 a and 16 b are connected to each other through avia hole conductor 13 c. The feeding terminal 15 b is connected to oneend of the loop-shaped conductor 12 and the feeding terminal 16 a isconnected to one end of the loop-shaped conductor 11. The feedingterminals 15 a and 16 a are connected to a feeding circuit, which is notillustrated. The feeding circuit, which is preferably a known circuit,for example, is defined by a semiconductor integrated circuit devicethat includes signal processing circuits, such as an RF circuit and abaseband (BB) circuit. Note that one of the feeding terminals 15 a and16 a of the loop-shaped conductor 11 may be grounded so as to enableunbalanced feeding.

The booster conductor 20 preferably includes a coupling conductorportion 21 and a frame-shaped radiation conductor portion 25. Thecoupling conductor portion 21 includes a second opening 22 that isoverlapped by the coil conductor 10 in plan view. The coupling conductorportion 21 is split in a portion thereof by a slit 23 and iselectromagnetically coupled to the coil conductor 10. In other words,the first opening 14 overlaps the second opening 22 in plan view. Theframe-shaped radiation conductor portion 25 includes a third opening 26and is connected to the coupling conductor portion 21 at two points.

The coil conductor 10 and the booster conductor 20 are preferably madeof, for example, a metal foil, metal thin film, or metal thick film in apredetermined shape on an insulating layer, which is not illustrated. Ametal thin film may be formed by patterning using photolithography oretching, or a conductive paste may be printed using screen printing, forexample.

In the antenna device 1A, the coil conductor 10 is electromagneticallycoupled to the coupling conductor portion 21, and a high frequencysignal is transmitted/received between a feeding circuit and the boosterconductor 20. In detail, as illustrated in FIGS. 2A and 2B, an inducedcurrent a flows circularly through the coil conductor 10 (loop-shapedconductors 11 and 12) connected to the feeding circuit, and the inducedcurrent a causes an induced current c to be generated in theframe-shaped radiation conductor portion 25 via an induced current bflowing through the coupling conductor portion 21. Note that the inducedcurrent c flows in a concentrated manner in the same direction in theinner peripheral end portion and outer peripheral end portion of theframe-shaped radiation conductor portion 25. Since the couplingconductor portion 21 includes the slit 23 provided therein, a potentialdifference is generated in the induced current b generated in thecoupling conductor portion 21, and the coupling conductor portion 21 andthe coil conductor 10 are coupled to each other. Further, a magneticfield is generated from the frame-shaped radiation conductor portion 25,and communication with the reader/writer of an RFID system is performed.A high-frequency signal radiated from the antenna of the reader/writeris transmitted to the feeding circuit in the opposite direction throughthe path described above. Note that the coil conductor 10 is illustratedas a single-layer conductor in FIG. 2 for simplicity.

Since the booster conductor 20 is overlapped in plan view by the coilconductor 10 in the coupling conductor portion 21, the induced currentsa and b are efficiently generated, whereby communication characteristicsare improved. In particular, since the radiation conductor portion 25 ofthe booster conductor 20 has a frame shape, a decrease in the Q factordue to the closeness of conductors is prevented and the communicationcharacteristics are improved. In a booster conductor 20′ illustrated inFIG. 3 as a comparative example, the frame-shaped radiation conductorportions 25 are disposed on both sides of the coupling conductor portion21 so as to surround the entire periphery of the coil conductor 10. Alsoin this case, the booster conductor 20′ is overlapped by the coilconductor 10 in the coupling conductor portion 21 in plan view. When theframe-shaped radiation conductor portion 25 surrounds the entireperiphery of the coil conductor 10, the Q factor of the coil conductor10 is decreased. However, since the frame-shaped radiation conductorportion 25 is arranged on only one side of the coil conductor 10 in theantenna device 1A, a decrease in the Q factor of the coil conductor 10is relatively small.

The manner in which the coil conductor 10 overlaps the couplingconductor portion 21 has a subtle influence on the electromagneticcoupling between the two conductors and the manner in which the inducedcurrent b is generated. The coil conductor 10 may completely overlap thecoupling conductor portion 21 in plan view or a peripheral portion 10 aof the coil conductor 10 may protrude toward the third opening 26 sidebeyond a peripheral portion 21 a, as illustrated in FIG. 2C, forexample.

The communication characteristics of the antenna device 1A areillustrated in FIG. 4. As a comparative example, the communicationcharacteristics of the antenna device 1A′ illustrated in FIG. 5 are alsoillustrated in FIG. 4. The antenna device 1A′, as a comparative example,has a configuration in which the booster conductor 20 has been replacedby a solid radiation conductor portion 25′, that is, a configuration inwhich the third opening 26 is filled with a metal material. Usually, thesolid radiation conductor portion 25′ is configured to function as anantenna in this manner, and this configuration has favorablecommunication characteristics as illustrated by a dotted line in FIG. 4.On the other hand, the antenna device 1A according to the presentpreferred embodiment, although preferably configured as a frame-shapedradiation conductor portion 25, has communication characteristics thatare substantially equivalent to those of the antenna device 1A′.

In the antenna device 1A, since the radiation conductor portion 25preferably has a frame shaped (the third opening 26), information can beinput/output through the third opening 26. Further, since almost nomagnetic field is generated in the third opening 26, communicationcharacteristics are not deteriorated even when a metal component isarranged within the third opening 26. This is an advantage which thecomparative example (antenna device 1A′) illustrated in FIG. 5 does nothave.

In other words, it is possible to take a photograph through the thirdopening 26 by arranging a camera in the third opening 26, infraredcommunication with the outside is possible through the third opening 26by arranging an infrared communication apparatus in the third opening26, and audio messages, for example, can be transmitted to the outsidethrough the third opening 26 by arranging a loud speaker in the thirdopening 26. In this manner, by arranging an electronic apparatus in thethird opening 26 to output information to the outside or receiveinformation from the outside, high-density component mounting in aportable terminal apparatus is achieved without significantlyinfluencing the operation of the electronic apparatus.

FIG. 6 illustrates the major portions of a portable terminal apparatusinto which the antenna device 1A is incorporated. The antenna device 1Ais preferably mounted on a substrate 30 of a portable terminal apparatuswith the booster conductor 20 being arranged on the upper side,electronic apparatuses 31 and 32, such as a camera, an infraredcommunication apparatus, and a loud speaker, for example, are preferablyarranged within the region of the third opening 26.

Another antenna device 35 is arranged next to the radiation conductorportion 25. The antenna device 35 is the main antenna of the portableterminal apparatus. When the antenna device 35 is arranged close to thesolid radiation conductor portion 25′ illustrated in FIG. 5, thecommunication characteristics of the antenna device 35 are deteriorated.However, in the antenna device 1A of the present preferred embodiment,since the radiation conductor portion 25 has a small conductor area,interference with the antenna device 35 is small and, thus, thecommunication characteristics of the antenna device 35 are notdeteriorated even when the antenna device 35 is arranged next to theradiation conductor portion 25.

By using the antenna device 1A, since the electronic apparatuses 31 and32 can be arranged in the third opening 26 and the antenna device 35 canbe arranged close to the antenna device 1A, the component mountingdensity in the portable terminal apparatus is greatly increased.Further, when these electronic apparatuses include a member made of amagnetic material, such as ferrite, or a metallic magnetic material,such as Fe, Ni, or MgO, for example, the communication range can befurther increased because the magnetic flux density in the third opening26 is increased.

Modification of Antenna Device

Referring to FIG. 7, a magnetic sheet 41 (preferably, ferrite sheet) maypreferably be pasted to the coil conductor 10 side of the antenna device1A. By using the magnetic sheet 41, a magnetic field generated in thecoupling conductor portion 21 is prevented from leaking to the coilconductor 10 side, whereby the strength of a magnetic field radiatedfrom the frame-shaped radiation conductor portion 25 is increased and,thus, the communication characteristics are further improved.

Modification of Coil Conductor

Referring to FIG. 8, the coil conductor 10 may preferably include only asingle-layer loop-shaped conductor 18. In this case, the two endportions of the loop-shaped conductor 18 define feeding terminals 18 aand 18 b, and are connected to a feeding circuit. Note that the numberof turns of the loop-shaped conductor 18 may be any suitable number.

Second Preferred Embodiment

Referring to FIGS. 9A and 9B, an antenna device 1B according to a secondpreferred embodiment of the present invention preferably includes aframe-shaped radiation conductor portion 25 that is connected to twopoints located on a diagonal line of a square-shaped coupling conductorportion 21. A coil conductor 10 is overlaid on the coupling conductorportion 21 as a single-layer loop-shaped conductor 18 that is preferablywound in a square shape, for example. The two ends of the loop-shapedconductor 18 define feeding terminals 18 a and 18 b. The antenna device1B has the same or substantially the same operations and advantages asthe antenna device 1A.

Third Preferred Embodiment

Referring to FIGS. 10A and 10B, an antenna device 1C according to athird preferred embodiment of the present invention preferably includesa coil conductor 10 and a coupling conductor portion 21 that aresubstantially L-shaped, for example, and are superposed with each other.The coil conductor 10 is defined by a single-layer loop-shaped conductor18, and the two ends of the loop-shaped conductor 18 define feedingterminals 18 a and 18 b. The antenna device 1C also has the same orsubstantially the same operations and advantages as the antenna device1A.

Fourth Preferred Embodiment

Referring to FIGS. 11A and 11B, an antenna device 1D according to afourth preferred embodiment of the present invention preferably includesa frame-shaped radiation conductor portion 25 that is configured in theshape of a coil. Other configurations are the same or substantially thesame as the antenna devices 1A and 1B. The antenna device 1D also hasthe same or substantially the same operations and advantages as theantenna device 1A. In particular, in the antenna device 1D, theresonance frequency of the frame-shaped radiation conductor portion 25can be set to be close to 13.56 MHz, which is the best frequency for usein an RFID system, by adjusting the shape of the coil conductor 10 andthe electrical length and the inter-line capacitance of the frame-shapedradiation conductor portion 25.

Fifth Preferred Embodiment

Referring to FIG. 12, an antenna device 1E according to a fifthpreferred embodiment of the present invention preferably includes a coilconductor 10 and a booster conductor 20 which both have a two-layerstacked structure, and is preferably formed by evaporating aluminum ontothe top and bottom surfaces of an insulating sheet, which is notillustrated, such as a PET film, for example.

The coil conductor 10 includes loop-shaped conductors 11 and 12 that arewound so as to be superimposed with each other in plan view andconnected to each other at the ends thereof by a via hole conductor 13a, thereby forming a single coil, and first openings 14 are provided atthe winding centers. An end of the loop-shaped conductor 11 is connectedto a feeding terminal 15 a, and a feeding terminal 16 b connected to anend of the loop-shaped conductor 12 is connected to a feeding terminal16 a through a via hole conductor 13 b. The feeding terminals 15 a and16 a are connected to a feeding circuit, which is not illustrated.

The booster conductor 20 preferably includes a second opening 22, acoupling conductor portion 21 including a slit 23, and a frame-shapedradiation conductor portion 25 that is configured in the shape of a coiland includes a third opening 26. The frame-shaped radiation conductorportions 25 including two layers are not electrically connected to eachother, and are electromagnetically coupled to each other. The coilconductor 10 and the coupling conductor portion 21 (the first opening 14and the second opening 22) are arranged so as to be superposed with eachother in plan view.

The antenna device 1E has the same or substantially the same operationsand advantages as the antenna device 1A. Further, since each of the coilconductor 10 and the booster conductor 20 has a two-layer stackedstructure, coupling between the two is increased, whereby communicationcharacteristics are further improved.

Note that communication terminal apparatuses and antenna devicesaccording to preferred embodiments of the present invention are notlimited to the above-described preferred embodiments, and variousmodifications are possible within the scope of the invention.

For example, instead of a feeding circuit, a wireless IC chip thatprocesses a predetermined high-frequency signal may be connected to thefeeding terminals of a coil conductor. The antenna device may be mountedon various communication terminal apparatuses, such as an IC card, otherthan a cellular phone, for example.

As described above, preferred embodiments of the present invention areuseful in communication terminal apparatuses and antenna devices. Inparticular, preferred embodiments of the present invention areadvantageous in that communication characteristics are improved andother electronic apparatuses can be arranged with high space efficiency.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. (canceled)
 2. An antenna device comprising: a coil conductor definedby a wound loop-shaped conductor and including a first opening at awinding center and two ends which are connected to a feeding circuit;and a booster conductor including: a coupling conductor portion thatincludes a second opening overlapped at least partially by the firstopening, is split in a portion thereof by a slit, and is coupled to thecoil conductor; and a radiation conductor portion that includes a thirdopening and is connected to the coupling conductor portion; wherein thethird opening is arranged at only one side of the second opening whenthe antenna device is viewed in plan view.
 3. The antenna deviceaccording to claim 2, wherein the antenna device includes only one thirdopening.
 4. The antenna device according to claim 2, wherein theradiation conductor portion is arranged on only one side of the coilconductor.
 5. The antenna device according to claim 2, wherein thecoupling conductor portion is not arranged at a center of the radiationconductor portion.
 6. The antenna device according to claim 2, whereinthe radiation conductor portion is connected to the coupling conductorportion at two points.
 7. The antenna device according to claim 2,wherein the coil conductor includes a plurality of layers and insulatorsdisposed between the plurality of layers.
 8. The antenna deviceaccording to claim 2, wherein the booster conductor includes a pluralityof layers and insulators disposed between the plurality of layers. 9.The antenna device according to claim 2, wherein a magnetic sheet isarranged on a coil conductor side of the antenna device.
 10. The antennadevice according to claim 2, wherein the radiation conductor portion hasa frame shape.
 11. The antenna device according to claim 2, wherein atleast a portion of the second opening is arranged directly adjacent toand along an outer peripheral edge of the booster conductor.